Hydrogen Embrittlement Processes and Al/Al_2O_3 Hydrogen Resistance Coatings of NdFeB Magnets

After analyzing the phenomena and processes of hydrogen embrittlement of NdFeB permanent magnets, RF magnetron sputtering was used to fabricate Al thin films and then oxidized to form the Al/Al_2O_3 composite films on the magnets as the hydrogen resistance coatings. SEM and EDS were used to examine the morphology and composition respectively. Hydrogen resistance performance was tested by exposing the magnets in 10 MPa hydrogen gas at room temperature. The results show that the magnets with 8 μm Al/Al_2O_3 coatings can withstand hydrogen of 10 MPa for 65 min without being embrittled into powder. The samples with and without hydrogen resistance coatings have almost the same magnetic properties.

Hydrogen permeation resistance and characterization of Si–Al and Si–Zr composite sol oxide coating on surface of zirconium hydride

The hydrogen permeation resistance of Si–Zr(SZ) and Si–Al(SA) composite sol oxide coating on zirconium hydride blocks(Zr H) was studied. SZ and SA composite sol were prepared by sol–gel method. SZ and SA composite oxide coatings were prepared on the surface of Zr H(in situ oxidized or not) in turns by dip-coating and heat treatment. Hydrogen permeation of Zr Hwith and without composite oxide coating was compared.Hydrogen desorption experiments in thermal vacuum show that hydrogen permeation resistance of SA composite oxide coating is better than that of SZ, to a certain extent,which could decrease hydrogen thermal loss. Experimental results in the working condition show that the SA composite oxide coating can not only prevent hydrogen permeation, but also retard contact and reaction between COand Zr Hmatrix, which could mitigate excessive oxidation of in situ oxide film. Differential scanning calorimetry and thermogravimetry(DSC–TG) analysis was performed to investigate the decomposition behavior of SA and SZ liquid sol in heat treatment process. X-ray diffraction(XRD) and scanning electron microscopy(SEM) analysis were employed to characterize the phase composition,surface and cross-section morphology of the coatings.

Effects of Hydrogen Ion Implantation on TiC-C Coating of Stainless Steel

Titanium carbide coatings are widely used as various wear-resistant material. The hydrogen erosion resistance of TiC-C films and the effect of hydrogen participation on TiC-C films were studied. Seventy-five percent TiC-C films are prepared on stainless steel surface by using ion mixing, where TiC-C films are deposited by rf magnetron sputtering followed by argon ion bombardment. The samples are then submitted to hydrogen ion implantation at 1.2 × 10^-3 Pa. Characterization for the 75% TiC-C films was done with SIMS, XRD, AES, and XPS. Secondary ion mass spectroscopy （SIMS） was used to analyze hydrogen concentration variation with depth, X-Ray diffraction （XRD） was used to identify the phases, and Auger electron spectra （AES） as well as X-ray photoelectron spectra （XPS） were used to check the effects of hydrogen on shifts of chemical bonding states of C and Ti in the TiC-C films. It is found that TiC-C films on stainless steel surface can prevent hydrogen from entering stainless steel.

Effect of Ti(C,N)Precipitation on Texture Evolution and Fish-Scale Resistance of Ultra-Low Carbon Ti-Bearing Enamel Steel

The Ti（C,N）precipitation and texture evolution in ultra-low carbon Ti-bearing enamel steel were studied to discover their correlation.Two different cooling paths of simulative coiling were adopted to gain different morphologies of Ti（C,N）precipitate in hot strips.It is found that the Ti（C,N）precipitate in hot strip using Path 2（put into asbestos box and air cooled）are finer and much more in quantity than that in hot strip using Path 1（held at 730℃ for 30min and furnace cooled）.The morphology of Ti（C,N）precipitate in hot strip has great effect on recrystallization texture in the subsequent cold-rolled annealed sheet.γ-fiber texture of strong recrystallization is gained in coldrolled and annealed sheet came from Path 1.On the contrary,in the one came from Path 2,theγ-fiber texture is weak.This may be due to the pinning force of numerous fine Ti（C,N）precipitate which retard the growth of preferential nucleated{111}orientated grains.Annealed steel sheets in the test came from both paths have excellent fishscale resistance.

Relationship between microstructure and hydrogen induced cracking behavior in a low alloy pipeline steel

Hydrogen induced cracking（HIC） behaviors of a high strength pipeline steel with three different microstructures, granular bainite ＆ lath bainite（GB ＋ LB）, granular bainite ＆ acicular ferrite（GB ＋ AF）, and quasi-polygonal ferrite（QF）, were studied by using corrosion experiment based on standard NACE TM0284. The HIC experiment was conducted in hydrogen sulfide（H_2S）-saturated solution. The experimental results show that the steel with GB ＋ AF and QF microstructure present excellent corrosion resistance to HIC, whereas the phases of bainite lath and martensite/austenite in LB ＋ GB microstructure are responsible for poor corrosion resistance. Compared with ferrite phase, the bainite microstructure exhibits higher strength and crack susceptibility of HIC. The AF ＋ GB microstructure is believed to have the best combination of mechanical properties and resistance to HIC among the designed steels.